Not the return address -- Cathy Sadler had been corresponding with her old fifth-grade teacher for several years, so she recognized the address of the retirement community in Dublin, Ohio.

But when Sadler, who lives in North Carolina, opened the envelope, she found something she wasn't expecting.

It was a photocopy of an old Mother's Day card.

There were many signatures on the card. She found her own name among them. She was Cathy Holt back then, a fifth-grader at Montrose Elementary School in Bexley, Ohio.

Miss Twyford had been the teacher. That's how all of her students, all of the 10- and 11-year-olds in that 1958 classroom, referred to her. Geraldine Twyford was her full name.

Bob Greene

"She's still Miss Twyford to me," Cathy Sadler, now 65, told me the other day. "She was such a wonderful teacher -- she brought such excitement and enthusiasm to her job. You could tell she wasn't just going through the motions. She loved teaching. My own love of history started in that classroom."

Her admiration for Miss Twyford is what led Sadler to seek her out and start writing to her. At 86, Miss Twyford chooses not to use e-mail -- she writes her letters in elegant longhand.

The old card -- the kind you would buy at a drugstore-- featured the embossed message: "You're such a sweet person, So thoughtful and kind, That days such as this, Always bring you to mind. Happy Mother's Day."

Surrounding those words were all the signatures -- written neatly in fountain pen, in children's script. The names were of the students in Miss Twyford's class: Arloa Shultz, Kent Kellner, Paula Young, Susan Bryant, Joe Sebring, Sherry Lamp, Maury Topolosky, many more. There was the signature of one child -- Alan (Peewee) Meyers, is what he wrote -- a sprightly, friendly boy who, three years later, would lose his life in an automobile accident.

Miss Twyford, in 1958, was unmarried and had no children. Yet the boys and girls had decided to present her with the Mother's Day card.

And she had saved it for all these years.

I called her last week at the retirement community in Ohio. She has been a widow since 2011; at age 39 she married Bob Ferguson, an electrical engineer in the aeronautics field, and they remained wed for 46 years until his death. "I'm not Mrs. Ferguson to my old students," she said. "I'm always Miss Twyford. Which is fine with me."

Geraldine Twyford Ferguson

I asked her about the card.

"I was surprised, and so touched, that they would give that to me," she said. She said that she had kept it in a "treasure chest" -- a footlocker where she has preserved all of her most precious memories.

"To me, the card meant that the boys and girls knew how much I cared for them," she said. "As a teacher, you always hope that you mean something to the children, and you hope that they understand how much they matter to you.

"As I look at the card from time to time, I see also that it is a sign that we accomplished one of our goals that year. In the fifth grade, students were expected to learn how to write in cursive, in ink. When you use ink, in a fountain pen, there is no erasing, no way to cover your mistakes. So I think they were showing that to me, too."

She told me that she grew up an only child in Gratiot, Ohio, a town of just 250 people. She said that a career teaching fifth grade -- she spent 30 years doing it -- was a full and satisfying way to spend her life. At Montrose Elementary, where she taught for 16 of those years, she said her classroom was on the top floor, overlooking Main Street.

"It was Route 40," she said. "The old National Road. I would tell the boys and girls to look out the window at the cars on the street, and to try to imagine the covered wagons moving west all those years ago, right there, carrying people who had left everything behind to start a new life."

The main reason she has kept the Mother's Day card, she said, was a simple one:

"I never had children of my own.

"It is the only Mother's Day card I ever received."

She said that, as a teacher, "You sometimes look out into your classroom and silently think, 'I wonder what will happen to them when they grow up.' "

Fifty-five years later, it is a Sunday in May again.

She is 86, and on her own.

In those 30 years of teaching, more than 700 boys and girls moved through her classrooms.

I know every person who signed that card; I know those who are living, and I knew those who have passed away.

And on this, I think I can safely speak for all of them.

The words on the card still hold true:

". . .So thoughtful and kind, That days such as this, Always bring you to mind."